In a potentiometer experiment, it is found that no current passes through the galvanometer when the
terminals of the cell are connected across 52 cm of the potentiometer wire. If the cell is shunted by a
resistance of 5Ω, a balance is found when the cell is connected across 40 cm of the wire. Find the internal
resistance of the cell.

2.5 Ω

1 Ω

1.5 Ω

2 Ω

Solution

1.5 Ω

When the cell is shunted by a resistance of 5Ω

$i = \frac{ε}{5 + r} N o w, \frac{ε - i r}{ε} = \frac{40}{52} \frac{r}{5 + r} = \frac{3}{13} ∴ r = 1.5 Ω$

For Daily Free Study Material Join wiredfaculty